last time I looked the S&S were as much money as a good folding bike ! I might be wrong , but you will need to pay a frame builder to install them, than repaint etc etc ...
Dahon Dash ... careful in the US Dahon sold most of them as unfoldable and only a few with the folding mechanism ... big difference in size
I would suggest a Tern Node D 8 with its 24 inch wheels its a good riding bike and can do 100 milers pretty comfortable.